Open Transactions can use it as a master identity to validate your revokable nyms with. Though it can also use various other methods or you can just use the nym's hash directly without layers of signers validating it like a certificate authority.
This method of using namecoin as similar to a certificate authority is kind of generic too, you can use it for various things, like open signon systems to sign on to multiple sites and stuff like that.
-MarkM-
That's something that I didn't know thanks! Pretty significant use other than .bit domains.
